Polyurethane-based engine covers protects pedestrians


People traveling on foot in traffic apparently live dangerously. According to the European Commission, about one-fifth of all traffic fatalities in Europe involve pedestrians. Apart from passenger protection, auto manufacturers therefore are also taking a closer look at pedestrian safety. 

The Volvo Car Corp. is a leader in the field, using a combination of Bayer MaterialScience (Leverkusen, Germany) materials to manufacture the engine covers, or hoods as the company refers to them, of its four cylinder diesel engines. Two special polyurethane systems provide for a soft "landing" in the event of impact with the hood: the resulting engine hood is elastic, acting as a crumple zone to reduce the effects of impact. The automaker also takes other measures to ensure pedestrian protection.

Volvo Car was in search of an all-around material that offers greater safety for pedestrians, dampens engine noise and can be efficiently processed. The Bayer MaterialScience Oldenburg systems house accepted the challenge: in close cooperation with Czech parts manufacturer Promens Zlin (Zlin, Czech Republic) and Volvo Car, it developed a material solution specifically for this application based on a combination of new grades of its Baytec and Bayfit polyurethane systems. 

The three partners cooperated throughout the entire development process, from selecting the raw materials and formulating the products, all the way to optimizing the reaction injection molding (RIM) manufacturing process. In production, the spray elastomer Baytec enters the mold first. It is responsible later on for the desired stability and smooth surface of the parts. The foam system Bayfit is then added to the same mold. Its job is to effectively dampen engine noise. The sandwich structure of these two materials is elastic and represents a great advancement in pedestrian protection. With it, Volvo Car has reportedly set new standards in safety, quality and comfort.

The engine hoods are manufactured in two basic versions: while the engines in standard vehicles are equipped with a black hood, the hybrid cars have a silver-colored version. Production of the silver-colored parts begins with the application of an in-mold coating. In the same mold, the subsequent processing steps are then carried out as described above.

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